Various building or similar structures have been proposed which are based upon column-like elements or rods used as basic construction units which function as stays. A fabric covering is usually associated with the network of rods employed. Also, it is usual for such assemblies to have foldable/extensible capability so that they may be extended/erected where desired and, when necessary, folded up to a rather compact form for storage and/or transportation. Other structures of this general nature are intended to remain in place once erected and within this category are what is known as geodesic structures.
Generally speaking, where the structures are intended to remain in place once erected, the rods or column-like element are rigidly joined together, whereas for the extensible/foldable structures these rods ordinarily are joined pivotally. Examples of extensible/foldable structures are found in the Pinero Pat. No. 3,185,164, the Greenberg et al Pat. No. 3,496,687 and the Kelley et al Pat. No. 3,710,806.
The patents are exemplary of the fact that the prior art in order to achieve an extensible/foldable capability has found it necessary to resort to various types of extraneous locking means. For example, in the Pinero patent not only is a system of cables a,b necessary to form the extended shape of the structure, but cables c are also required to hold such shape (i.e., to render the structure self-supporting). The Kelley et al patent represents another basic approach and that is to provide hub-connected scissors linkages.
In all of the prior art devices, except in those instances where positive locking means are used, the structural integrity of the extended, erected structure is not great and none employs an arrangement wherein structural integrity results from a relationship among the rod-like elements which is attained by and incidental to the erected shape itself and which does not rely upon physical constraint of the pivotal connections among the rod elements.